The present invention relates generally to a surgical instrument and a method for treating female urinary incontinence and in particular to a conical needle for facilitating the perforation of different layers of tissue, with each tissue layer having a different resistance against perforation.
Women account for more than 11 million of incontinence cases. Moreover, a majority of women with incontinence suffer from stress urinary incontinence (SUI). Women with SUI involuntarily lose urine during normal daily activities and movements, such as laughing, coughing, sneezing and regular exercise.
SUI may be caused by a functional defect of the tissue or ligaments connecting the vaginal wall with the pelvic muscles and pubic bone. Common causes include repetitive straining of the pelvic muscles, childbirth, loss of pelvic muscle tone, and estrogen loss. Such a defect results in an improperly functioning urethra. Unlike other types of incontinence, SUI is not a problem of the bladder.
Normally, the urethra, when properly supported by strong pelvic floor muscles and healthy connective tissue, maintains a tight seal to prevent involuntary loss of urine. When a woman suffers from the most common form of SUI, however, weakened muscle and pelvic tissues are unable to adequately support the urethra in its correct position. As a result, during normal movements when pressure is exerted on the bladder from the diaphragm, the urethra cannot retain its seal, permitting urine to escape. Because SUI is both embarrassing and unpredictable, many women with SUI avoid an active lifestyle, shying away from social situations.
U.S. Pat. No. 5,112,344 describes a method and apparatus for treating female incontinence. The surgical instrument for the application of a filamentary element into the body comprises a tubular shaft having a handle at one end and a flexible needle slidably receivable in the shaft and adapted at one end to receive a filamentary element. The method of treating female incontinence comprises looping a filamentary element between the wall of the vagina and the rectus abdominis sheath in the anterior wall of the abdomen whereby it passes to each side of the urethra, tightening the loop to bring the vaginal wall the urethra into the correct spatial relationship to the pubis allowing the development of scar tissue between the vaginal wall and the anterior wall of the abdomen pubic symphysis and removing the filamentary element.
U.S. Pat. No. 5,899,909 discloses a surgical instrument comprising a shank having a handle at one end and connecting means at the other end to receive, one at a time, two curved needle-like elements which are connected at one end to one end of a tape intended to be implanted into the body. In practice, the tape is passed into the body via the vagina first at one end and then at the other end at one side and the other, respectively, of the urethra to form a loop around the urethra, located between the urethra and vaginal wall. The tape is extended over the pubis and through the abdominal wall and is tightened. The tape ends are cut at the abdominal wall, and the tape is left implanted in the body.
Current needles for implanting tapes have a short conical tip and a curved body with a constant diameter. When the conical needle tip perforates a layer of human tissue having a high resistance against perforation (like fascia or muscle), the force required is high compared to the force required to perforate soft human tissue (like fat). To lower the maximum force required by the surgeon to penetrate fascia or muscle, the needle tip is pointed. After the conical tip passes through a tissue layer with a high perforation resistance, however, the force required to further pass the needle through the tissue suddenly drops close to zero. As an undesirable consequence then, the needle may penetrate through tissue faster than the surgeon intends, possibly causing the surgeon to lose control of the needle and risking the possibility of unintentionally perforating other body structures, such as, bone, organs or blood vessels, with the pointed needle tip.
It would be beneficial to provide a needle for use in implanting a mesh tape within a female body to prevent incontinence that has a design that provides for a more even resistance for perforating differing types of tissue.
It would also be beneficial to simplify the design of the surgical instrument to facilitate the loading of the tape onto a needle during the operation. In this manner, the instrument would be more receptive to various types of tapes, such as synthetic, cadaver tissue and engineered tissue.